The long term objective of this project is to provide a link between PDT experiments performed under controlled conditions in the laboratory, and the implementation of these results into clinical settings. Two specific goals will addressed. The first goal will be to begin to define tumor and treatment related factors that have prognostic significance in the clinical setting. The treatment related factors to be evaluated are light fluence and photosensitizer uptake. These factors will be measured in both tumor and surrounding normal tissue. The physiologic state of the tumor will be assessed by MRS parameters (Ph, Pi, Pcr, PME, PDE, and NTP) both prior to and sequentially after PDT. MRS parameters, light fluence and photosensitizer uptake will be evaluated for their correlations with initial tumor response, response duration, and long term local control. The second goal is to determine which of three representatives of different classes of photosensitizers, Photofrin II, benzoporphrin derivative (BPD), or aluminum sulfonated phthalocyanine (ALSPc), can achieve the greatest differential between tumor control and normal tissue toxicity ("therapeutic gain"). Two steps will be necessary to achieve this goal. A maximally tolerated dose must be established for each drug, and then equally toxic doses will be tested to determine which drug can achieve the greatest antitumor effect. Since toxicity is fixed at a defined level, the agent with the greatest antitumor effect will define the one with the greatest therapeutic gain. Spontaneous large animal tumors are particularly suited to providing a link between laboratory experiments and clinical applications. They demonstrate many characteristics similar to those observed in man, including their natural history, biologic behavior, vascularity, inherent heterogeneity, size, location and histology. Spontaneously occurring canine squamous cell carcinomas and soft tissue sarcomas will be the animal models used to pursue these objectives.